G.R. Wiggans,*1 S. Tsuruta,† and I. Misztal†
*Animal Improvement Programs
Laboratory, Agricultural Research Service, USDA, Beltsville, MD
20705-2350
†Department of Animal and Dairy Science, University of
Georgia, Athens 30602
2007 J. Dairy Sci. (?)
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The ACCF90 computer program, which approximates reliability for animal models, was modified to estimate reliabilities for sire-maternal grandsire (MGS) models. Accuracy of the approximation was tested on a calving-ease data set for 2,968 bulls for which the inverse of the coefficient matrix could be obtained. Correlations between estimated and true reliabilities ranged from 0.984 to 0.998 for first- and later-parity calving ease for sire and MGS effects. Without modification, the program treated MGS data as though they were dam data, which resulted in overestimated reliability. When pedigree data were ignored, reliability was underestimated. Correlations with true values were lower for both those cases when compared with correct processing of MGS data. The modification provided a slight improvement over assuming MGS to be unknown. The modified program will be used for routine USDA evaluation of calving traits.
(Key words: reliability, sire-maternal grandsire model)